Acetone 2,4-dinitrophenylhydrazone

A 0.1% solution of the reagent is prepared by dissolving 0.12 g, of 2,4-dinitrophenylliydrazine in 25 cc. of distilled water and 21 cc. of concentrated hydrochloric acid by warming on the steam bath. The clear yellow solution is then cooled and diluted to 125 cc. with distilled water. For use, several drops of the reagent and a few drops of the acetone-isopropyl alcohol distillate are mixed in a small test tube. The presence of acetone is shown by the formation of a yellow cloudy suspension or precipitate of acetone 2,4-dinitrophenylhydrazone. The test is considered negative if no cloudiness forms within one-half minute when 3 cc. of the reagent is added to 5 drops of distillate. After a negative test is obtained, it is advisable to reflux the mixture for five to fifteen minutes with complete condensation and then to force over a few drops of distillate for another test. If no acetone is observed, reduction is complete. Otherwise the process is continued until no more acetone can be detected. This procedure indicates complete reduction even with ketones which are reduced very slowly. 

From Geraniol. The geraniol used was purified in accordance with the method of Knights and Waight (5) and ozonized in pure methanol in the usual manner. The mixture of 2,4-dinitrophenylhydrazones obtained after reduction with sodium bisulfite was extracted with hot ethanol and the solvent removed. The residue was recrystallized from aqueous ethanol yield of acetone 2,4-dinitrophenylhydrazone, 40.8% melting point, 123-4° C. 

Acetone hydrazone (1.5 g, 0.02 mole) is dissolved in 95% ethanol (10 ml) and treated with a solution of l-chloro-2,4-dinitrobenzene (4.0 g, 0.019 mole) in 95% ethanol (30 ml). The mixture is heated for 1 h under reflux, then cooled and filtered. The solid product is freed from a little adhering chlorodinitrobenzene by washing with a little warm ethanol and is then dried. One recrystallization from 95 % ethanol gives acetone 2,4-dinitrophenylhydrazone, m.p. 123°. 

Separation of 2,4-dinitrophenylhydrazones. The solutions are prepared by dissolving 10 mg of each of the 2,4-dinitrophenylhydrazones of acetone, butan-2-one and hexan-3-one (or hexan-2-one) in 0.5 ml of ethyl acetate. Prepare a flexible silica gel sheet of dimensions 20 x 5 cm in the manner already described and apply c. 0.5 pi of each of the three solutions to give the marker spots of a diameter of between 2 and 3 mm. A mixed spot is conveniently obtained by loading sequentially to the same area further 0.5 pi aliquot portions of each of the solutions and allowing the solvent to evaporate completely between each addition. 

Dinitrophenylhydrazine is frequently used for making derivatives of ketones and aldehydes because the products (2,4-dinitrophenylhydrazones, called 2,4-DNP derivatives) are even more likely than the phenylhydrazones to be solids with sharp melting points. Propose a mechanism for the reaction of acetone with 2,4-dinitrophenylhydrazine in a mildly acidic solution. 

The only other commonly reported technique is the acid-catalysed evolution of nitrogen gas. Typically, sulphuric acid is used as the catalyst . This is not totally reliable, however. Coombsreports that if carbon-nitrogen cleavage will yield a stable carbonium ion, then formation of HN3 predominates over loss of N2 and formation of imine. This is contradicted, however, by the report that i-butyl azide in the presence of sulphuric acid yields acetone-A-methylimine which subsequently hydrolyses to give acetone, isolated as its 2,4-dinitrophenylhydrazone. 

Aldehyde and acetone derivatives show an absorption peak around 370 nm (Fig. 69). The absorptivities of derivatives (2,4-dinitrophenylhydrazone) increase notably as compared to carbonyl compounds, making their detection more easy (Table 6). 

Figure 69. Aldehydes and acetone derivatives from 2,4-dinitrophenylhydrazone (10 mgL 1).

Hydrazine too reacts with activated aryl halides as readily as ammonia or amines. The important carbonyl reagent 2,4-dinitrophenylhydrazine is obtained in 80% yield from an aqueous-alcoholic solution of l-chloro-2,4-dinitrobenzene and hydrazine.555 Moreover, hydrazones can be arylated in the same way, which can be of interest when the 2,4-dinitrophenylhydrazones cannot be prepared with ease directly from the ketone. The conversion of acetone hydrazone into the 2,4-dinitrophenylhydrazone556 will be described here as a typical example ... 

A mixture of palmitaldehyde 2,4-dinitrophenylhydrazone, levulinic acid, and BFg-methanol reagent (or methanolic 10%-HCl) refluxed 45 min. at 85°, cooled to 0°, 90%-methanolic 5 N NaOH added, and again refluxed 20 min. to saponify the methyl levulinate palmitaldehyde dimethyl acetal. Y 84%. Also with acetone (Y 77%) in place of levulinic acid s. V. Mahadevan, F. Phillips, and W. O. Lundberg, J. Lipid Research 6, 434 (1965). 

Cleavage of tosylhydrazones. A mixture of phenylacetone tosylhydrazone and Am-berlyst 15 in 10 1 acetone/water stirred at room temp, for 24 h phenylacetone. Y 91%. The method is applicable to aldehydes (especially in the presence of 10 eqs. of paraformaldehyde) as well as ketones it is simple and cheap furthermore, acid-sensitive groups such as furyl derivs., esters or ethers are not affected. F.e. incl. cleavage of oximes, 2,4-dinitrophenylhydrazones and semicarbazones, s. R. Ballini, M. Petrini, J. Chem. Soc. Perkin Trans. I 1988, 2563-5. 

In practice, eluents of widely varying polarity have been used. Very weakly polar steroids (oestrenols) can be quantitatively eluted with hydrophobic solvents like methylene dichloride (cf Table 14) [217], whereas difficulties are reported in the elution of the more polar progesterone under the same conditions [691]. Chloroform has been used to elute dinitrophenylhydrazones from silica gel and opium alkaloids from alumina [470, 535]. Methanol and ethanol are often used for elution of substances of all types of compound class from silica gel [213, 215, 259, 434] or alumina [122, 437]. Butyl acetate has been chosen as the most suitable eluent for penicillin V [486]. Acetone has proved suitable for recovering ubiquinones [733]. Polar neutral, acid and basic aqueous eluents have also been employed, e.g., water for mucic acid derivatives [451] (cf Table 14), 1% Tween 80 solution for cobalamin [128], 0.2 N sulphuric acid for Vitamin Bg factors [702], 34% ammonium persulphate solution for nicotinic acid [702] and ammonium hydroxide for azo dyes [638]. Nitro-4-acetaminophenetoles have been extracted from alumina with the highly polar dimethylformamide [489]. 

Fig. 103. Multiple development of homologous 2,4-dinitrophenylhydrazones on kieselguhr G-layers, impregnated with 10% phenoxyethanol-acetone solution [310]. Solvent petrol ether (BP 100 to 120° C). 1—3. 9 cm developments 4.11 cm development...

The separation by TLC of the 2,4-dinitrophenylhydrazone (DNP) of dehydroascorbic acid is extremely specific and has been employed for detection and determination of vitamin C in food and feeding stuffs, fats, fruit juices, wines and bacteria etc. In the method of Stroheckeb et al. [129, 130] the ascorbic acid in the extracts is oxidised with 2,6-dichlorophenol-indophenol (Vuilleumieb and Nobile [139] use bromine for this) the dehydroascorbic acid formed is then reacted for 3 hours at 70 C with 2,4-dinitrophenylhydrazine in the presence of a little trichloroacetic acid and thiourea [131]. After cooling 10 min in ice, the red or red-brown precipitate is collected on a sintered glass filter, washed with water and dissolved in ethyl acetate or acetone the solution is evaporated and the residue taken up in acetone. 0.1—1.0 ml (20 to 50 [xg vitamin C) of this solution is applied as a band to air dried silica gel H layers and chromatographed with chloroform-ethyl acetate (50 + 50) or, better, with chloroform-ethyl acetate-acetic acid (60 + 35 -f 5). The red DNP of the dehydroascorbic acid is thus clearly separated... 

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